Chapter 19 - Step 13

This is really plans step 12 part B. This step involves drilling 5/8" holes through the wing and spar hardpoints and adding LWA9 bushings.

Laying out the wings February 13, 2003. Once the pilot holes in the spar were made, it was time to layout the wings. This is a long and tedious process to get just right. Besides, you waste a bunch of time just staring at the two wings spread out on the floor. It's just so cool! Anyway, at this point I was going for more of a rough idea of how everthing layed out and fit. I just stacked some boards and added and shifted as needed to get everything pretty close. Here are a few suggestions that bit me at first:


Getting it level February 13, 2003. I finally got close enough to start checking that the wing incidence was level. I ran into two issues at this point.

For some reason, on the right wing/spar, the spar was hitting the wing rib so that the holes wouldn't line up. I had to sand down the outboard wing rib lip a little until the spar could be put in place properly. Wasn't much but I didn't have this on the left wing.

I also found that with everything lined up just as it should be, the top of the spar and top of the wing were uneven. I found that if I got the top of the wing and spar even at the outboard end of the spar, the top of the wing at the inboard hard points was higher than the spar top. I could correct the situation by adding about 9/16" more shims under the outboard tip of the wing. Doing this got the top of the wing and spar to line up. The bonus was that the bottom of the wing and spar now also lined up. The best part is that I need the same correction on the other wing too. So in the end I had both wings the same, 9/16" extra dihedral. Both had 0° incidence, and the match between the top and bottom of the spar and wing were such that I would need minimal filler. Since the plans state that dihedral is more esthetics than performance, I was OK with this compromise. I also confirmed with Nat that this was OK - he agreed. My theory is that I mismeasured either the wing or spar at some point during construction but at least I did it the same to both (luckily).

The bigger picture February 13, 2003. A bigger picture view of everything layed out in place. Later on I completely redid this using plastic storage bins under each end of the wings and under the spar to get everything higher off the floor - much better.

Lining up both trailing edges February 13, 2003. I had planned on using a water level for all of this but in the end I didn't. I did use a laser level though. Here I am using it to ensure both outboard trailing edge tips are at the same waterline - happily they were. I used this for each wing initially to get both ends even at the 17.4 waterline. This helped ensure both wings agreed with each other. My standard smart level was used to ensure 0° incidence on both wings and the spar.

Drilling holes February 13, 2003. I managed to do all my drilling without using any bondo. Once everything was lined up I used clamps to hold the wing to the spar. I then did all the drilling through the hard points. I used a 5/8" bi-metal hole saw, just like in chapter 9, to do the holes. The only issue here was that the hole saw wasn't quite long enough to go all the way through the spar and wing. So I drilled all three holes through the spar and part way into each wing. I then separated the spar from the wing and finshed all the wing holes.

More drilling February 15, 2003. Lots of small, aluminum donuts. I cleared the bit after getting through each layer of aluminum - and there are lots of layers times 6 holes.

Aligning wing and spar February 15, 2003. After drilling all the holes I placed the inserts into the holes and reassemled everything for one last test fit. I placed all the bolts in place to ensure all was lined up and then added the level board to each end of the spar.

Final test February 15, 2003. Ensuring the spar is level.

Numbering inserts February 18, 2003. I numbered all twelve holes and inserts so as I marked and cut them, I knew which insert went with which hole.

Measuring inserts February 18, 2003. I made a small measuring tool out of a piece of popsicle stick. The notch for the insert aligns perfectly with the "L" shape on the other side. All I did was place the wider end of the jig into the wing or spar hole and held the narrow end so the "L" hooked inside the hole. I then made a small pencil mark on the jig, removed it from the hole, placed one of the inserts as shown in the picture, and transferred the mark to the insert. I was surprised to find that many of the holes were the same depth. That's a good thing really.

Once I had all the inserts marked I cut them to length. I used a hacksaw to rough cut them to length. Maybe 1/32" long according to the pencil mark. I then filed them to the mark and test fit in the hole. I usally had to file a hair more to ensure it wasn't too long. I figure a few hundreths too short is much better than any amount too long.

Completed wings February 19, 2003. Here are the wings after I floxed in the inserts and reassembled everthing for cure. I was quite happy with how it all came out. For cure, I slid the six bolts into place to ensure the inserts were lined up just right. After cure, before I removed the clamps, five of the six bolts slid in and out holes with ease and the sixth went in and out with just the slightest extra weight pressed onto one wing end. I also ended up only needing one thin washer on the upper, outboard bolt of the left wing. Of course I could still have a nasty turn in the plane but for now, the wing/spar mating came out very well. Even though I did have to add a touch of dihedral to both wings, I don't think anyone will be able to tell.